CA1153008A - Herbicidally active phenoxy-phenoxy- alkanecarboxylic acid derivatives and use thereof for controlling grass-like weeds - Google Patents

Abstract

Abstract of the Disclosure The invention is concerned with new herbicidal active 4-(cyanophenoxy)-.alpha.-phenoxy-alkanecarboxylic acid derivatives of the type wherein R1 is hydrogen, halogen, CF3 or CN, preferably chlorine, R2 is preferably hydrogen, R3 and R4 is hydrogen or lower alkyl, preferably R4 is hydrogen and R3 is methyl, and R5 is an acid derivative, especially an ester group.
The invention is further concerned with herbicidal compositions containing such new derivatives and with methods for the selective control of grass-like weeds in crops of dicotyledonous and also monocotyledonous plants such as cereals.

Description

~ ~5 3~ ~ ~

The present invention provides novel herbicidally active, nuclear-substituted phenoxy-phenoxy-alkanecarboxylic acid derivatives, processes for their manufacture, herbicidal compositions which contain these novel compounds as active ingredients, and methods of selectively controlling grass-like weeds in crops of cul~ivated plants which comprises the use of the novel active substances or of compositions which contain them.
The novel active compounds have the formula I
O-C-CO-R5 ~I) wherein Rl represents hydrogen, halogen, the trifluoromethyl or cyano group, R2 represents hydrogen or halogen, each of R3 and R4 independently represents hydrogen or lower alkyl, and R5 represents a OH, -O-cation, -O-alkyl, -O-alkoxyalkyl, -S-alkyl, -S-alkenyl, -S-CH2-COO-alkyl, -O-alkenyl, -O-alkynyl, -O-cycloalkyl, -O alkyl-N(dialkyl) group, an unsubstituted or substituted benzyloxy, phenoxy or phenylthio radical, and NH2, NH-alkyl, -N(dialkyl), alkyl or -N~
O-alkyl.

- 2 -~ ~5 ~

Lower alkyl radicals represented by R3 and R4 are to be understood as meaning herein s~raigh~-chain or branched radicals containing 1 to 4 carbon a~oms. The alkyl-containing groups represented by R5 can contain a higher number of carbon atorns and have longer alkyl chains (up to 10 carbon atoms), preferably also in this case 1 to 6 or 1 to 4 carbon atoms. Corresponding alkenyloxy, alkenylthio and alkynyloxy groups contain up to 4 carbon atoms. Cycloalkoxy groups contain 3 to 12, preferably 5 or 6, carbon atoms.
Particularly preerred active compounds are those in which R4 is hydrogen and R3 represents hydrogen, ethyl and, in particular, methyl.
Possible substituents of phenoxy, phenylthio and benzyloxy groups R5 are one or more selected from the group consisting of halogen, alkyl and nitro.
By cations of the -O-cation group (represented by R5) are meant mono- and polyvalent cations of inorganic or organic bases, including quaternary ammonio bases, in particular the cations of alkali metal and alkaline earth metal hydroxides.
The preferred halogen atom represented by Rl and R2 is chlorine.
Herbicidal compositions containing 4-phenoxy-phenoxy-alkanecarboxylic acid derivatives of similar structure and having a special action on grass for the selective control of grass-like weeds in mono~ and dicotyledonous cultivated plants are known from D~-OS 2,223,894. Derivatives of these ~ ~ 3~ ~ ~

alkanecarboxylic acids which are trifluoromethylated in the para-position of ~he ~erminal phenyloxy radical have also been described (Belgian patents 831,218 and 831,~69).
The surprising discovery has now been made that, on account of the presence of ~he cyano substituent, the novel active compounds of the formula I of the present invention are clearly superior in their action on grass to the above mentioned active substances as a consequence ei~her of their better action against grass~like weeds and/or their better selectivity, for e~ample in soya and cotton.
Accordingly the active compounds of the invention are suitable for the preemergent and especially postemergent selective control of grass-like weeds (for example panic-grasses) of the genera Digitaria, Setaria, Echinochloa, Rottboellia, and also Alopecurus, Apera, Lolium etc. and especially also Avena fatua (wild oats), not only in crops of dicotyledonous cultivated plants (such as cotton, soya, sugar beet etc)., but in particular in crops of monocotylede-nous plants as well, such as cereals (wheat, barley, rye, oats), rice etc. In this respect, and especially for solving the problem of controlling wild oats in wheat, the novel active compounds and the compositions which contain them constitute a notable enrichment o the stock of technical knowledge.
Some of the active compounds of the invention also .. . . . . . . .

~ ~S 3~

possess advantageous growth-regulating effects (growth inhibition) .
Particularly preferred active compounds of the formula I
are those wherein R2 represents hydrogen and which contain a further substituent Rl in addition to the cyano group, such as in particular chlorine or the CF3 group. Moreover, it has been established that compounds in which the cyano group and Rl (if present) are in the ortho- or para-position have a particularly good action and selec~ivity. If Rl is chlorine, then compounds with ortho-cyano - para-chloro and ortho-chloro-para-cyano configuration have the best action. If Rl is hydrogen, the cyano group is preferably in the para-position.
Further important compounds are those in which R4 repre-sents hydrogen and R3 is different from hydrogen, for example lower alkyl, in particular methyl. The simplest ester form (R5 = OCH3) has outstandingly good activity.
The novel compounds of the formula I are obtained by the methods which are known per se for the synthesis of phenoxy-phenoxy-alkanecarboxylic acids and derivatives thereof.
In a first such process, according to the invention a substituted halogenonitrobenzene of the formula II

Rl ~ llal (II) CN

, . . . . .... ., ... ~

~ ~ 3~ ~ ~

is reacted with a p-hydroxy-phenoxy-alkanoic acid derivative of the formula III
R~
HO ~ O-C-CO-R5 ~III) - ~2 R3 in the presence of a base.
In a second process, according to the invention a substituted p-hydroxy-diphenyl ether of the formula IV

OH (IV) is reacted with an a-halogenoalkanoic acld derivative of the formula V

4 (V) Hal - C - CO - R5 in the presence of a base.
In a third process, the cyano group is introduced in the final process step. Accordingly, in this process a 4-(halogenophenoxy)-a-phenoxy-alkanecarboxylic acid derivative .~ ~ 6 -~ ~ 3 of the formula VI

1 ~ ~ O C-COR5 (VI) Hal R2 wherein Hal represents a halogen atom, such as a chlorine, bromine or iodine atom, is reacted with potassium or sodium cyanide in a polar solvent in the presence of a catalyst which activates the halogen atom, such as tetrakis (tri-phenylphosphine)-nickel (Ni~P(C6H5)3]4), preferably in a protective gas atmosphere (nitrogen, argon etc.) at tempera-turesbetw~n 20 and 120C, preferably between 50 and 70C, i.e. in analogy to the reactions described in Adv. Chem. Ser.
132, 252 (1974) and Journ. Organomet. Chem. 54, C 57 (1973).
If Rl represents halogen in the starting material of the formula VI, it is also possible to replace th;s further halogen atom by a cyano group.
If a carboxylic acid (R5 = OH) is used in these processes as starting material of the formulae III, V or VI, then this group can subsequently be converted into another derivative of the formula I as defined herein, for example by esterificat~

ion etc. Conversely, when using an ester of the formula III, V or VI, the ester group can subsequently be con~erted into the ~ree carboxylic acid or a salt thereof by saponification ~53~8 or into another ester by -~ransesterification.
In the formulae II to VI of the starting materials, the symbols Rl to R5 are as defined in formula I and Hal represents a halogen atom, s~lch as a chlorine or bromine atom.
The above reacti.ons can be carried nut in ~he presence or absence of solvents or diluents which are inert to the reactants. Polar organic solvents,such as methyl ethyl ketone, dimethyl formamide, dimethyl sulphoxide, alcohols, ketones etc., are preferred. The reaction temperatures are between 0 and 200C, and the reaction time is from 1 hour to several days, depending on the starting material, choice of reaction temperature, and solvent. The process is usually carried out at normal pressure. Suitable bases (condensation agents) for the reaction are those normally employed, for example KOH, NaOCH3, NaHC03, K2C03, potassium tert. butylate etc., and also organic bases, such as triethylamine etc.
The starting materials of the formulae II to VI are partly known. Starting materials of these formulae which have not yet been described can be easily prepared by conventional processes and techniques. Phenoxyphenols o the formula IV can be prepared from hydroquinonemonoalkyl ethers and monochloro-or dichlorobenzonitriles for example in accordance with the methods described in Journ. ~m. Chem. Soc. 61, 2702 (1939) or in Chem. Abstracts 5~, 92~h (1960).

., , , , ., . , ,,., .. , ., . ... . ., . , ~ .. ..... .. .. .

~ ~5 ~ O ~

The following Examples illustrate the process o the present invention. Further active compo~mds which are prepared in corresponding manner are listed in ~he su~sequent table.

9 _ - ~ .

~ ~ 3 Example 1 a) Preparation of the starting material:

A three-necked flask is charged at room temperature with 7 ~
of pulverised potassium hydroxide and 12.4 g of hydroquinone-monome~hyl ether in 300 ml of dimethyl sulphoxide. ~ith stirring and at a temperature between 15 and 20C, 17.2 g of dichlorobenzonitrile are added in small amounts and stirring is continued initially for one hour at room temperature. The reaction ~lixture is then heated for 12 hours at 70C. ~'or working up, the reaction mixture is poured into an ice-water mixture and the precipitated substance becomes solid after a time. The solid is collected with suction and recrystallised from methanol, affording 20 g of 2-cyano-~-chloro-(4'-methoxy-phenoxy)-benzene with a melting point of 101-102C.

A tllree-necked 1ask is charged, while introducing a flow of nitrogen, with 60 ml of glacial acetic acid and 25 ml of acetic anhydride. Thereafter 24 ml of 67% hydriodic acid are added dropwise while cooling with ice. The ambient temperature rises to 30C. The mixture is then heated to a bath temperature of 90C and 26 g of 2-cyano-4-chloro-(4'-metho~yphenoxy)-benzene are added in small amounts at this temperature. The bath temperature is raised to 120C and the reaction mixture is further stirred for 3 hours. ~fter cooling, the reaction mixture is poured into ice-water with vigorous stirring. The precipitate is collected with suction, washed with water and ~ ~ 3~ ~ ~

dried. Recrystallisation from benzene/pe~roleum ether yields 20 g of 2-cyano-4-chloro-(4'-oxy phenoxy)-benzene of the formula Cl ~ - ~ OH
~N

with a melting point of 105-107C.

b) A mixture of 20 g of this 2-cyano-4-chloro-(4'-oxy-phenoxy)-benzene, 18 g of methyl 2-bromo-propionate, 12 g of anhydrous potassium carbonate and 250 ml of methyl ethyl ketone is heated, with stirring, for 12 nours to reflux temperature.
After cooling, the reaction mixture is filtered and washed with methyl ethyl ketone. The filtrate is then concentrated in vacuo. The residual viscous oil is subjected to high vacuum distillation, affording 16 g of methyl 4-(2'-cyano-4'-chloro-phenoxy)-a-phenoxy propionate with a boiling point of 199-203C/O.Ol Torr.

Example 2 A two-necked flask is charged, in an atmosphere of argon, with 1.7 g of tetrakis-(triphenylphosphine)-nickel(O~ and a degassed solution of 8.5 g of methyl 4-(4'-chlorophenoxy)-~-phenoxy-propionate in 25 ml of absolute ethanol is added. The mixture is heated with stirring to 60C for 30 minutes. Then 1 g of sodium cyanide is added and stirring i9 continued for ... ... . . .. . .. . . , .. . .. ; .. . .. ..... . ...... . . .. ... .. . . ..

.

~ ~ ~ 3~ ~ ~

2 hours at 70C. Then a further 0.25 g of sodium cyanide is added and stirring is continued for a furt,her 2 hours at 70C, in the process of which a t ansesterification also takes place.
After the reaction mix~ure has cooled, it is filtered through "Hyflo" and the solvent is removed by rotary evaporation. The residual viscous oil is chromatographed over 200 g of silica gel with benzene/methylene chloride, yielding 2.5 g of ethyl 4-(4'-cyanophenoxy)-a-phenoxy-propionate as the very last raction; b.p. 171-174C/0.01.

The compounds of the above Examples as well as further active compounds of the formula I which are prepared in corresponding manner according to the invention are listed in the following table.

The listed compounds are those in which R2 and X4 represent hydrogen and which therefore have the narrower formula Rl ~ 0-CU C0-R5 CN

.

:~L53~

TABLE
_ .
Compound Position o~ Rl R3 R5 PhyOical constan-ts the CN group . . m.p C/b.p C/torr with posltlon _ ~
1 2-CN 4-Cl CH3 -ûC~13 b p 199-203 /0 01 2 4-CN H CH3 -OC2H5 b.p. 171-171 /0 01

3 2-CN -Cl H -OCH3 m.p. 119-120

4-CN 2-Cl CH3 -OCH3 b.P. 210 /0 002 4-CN H CH3 -OCH3 m.p. 64-65 6 2-CN 4-Cl CH3 -OH m.p. 154-155 7 2-CN 4-Br C~13 -OCH3 9 2-CN 4-Cl CH3 -OC2H5 b.p. 194 /0.05 2-CN H CH3 -OCH3 oil 11 2-CN 4-Cl H -OC2H5 m.p. 102-104 12 2-CN 4-Cl H -OC4Hg(n) oil 13 2-CN 4-Cl C2H5 2 5 oil 14 2-CN 4-Cl C~13 -NH2 m.p. 197 2-CN 4-Cl CH3 ( 2 5)2 oil 16 2-CN 4-Cl CH3 O-benzY' m.p. 113-115 17 2-CN 4-Cl C~13 -O-CH -CH=CH2 i ' 18 2-CN 4-Cl CH3 -O CH2CYCH oil 19 2-CN 4-Cl CH3 -0-C~I-CwCH2 i ' Cl 2-CN 4-Cl CH3 -O-Cil -C=CH2 i Cl~3 21 2-CN 4-Cl CH3 -N/ oi l Cl!H9( n ) 22 2-CN 4-Cl CH3 -oC3H7(rl) oi l 23 2-CN 4-Cl CH3 3 7( ) oil 24 2-CN 4-Cl CH3 -OC4Hg(n) b.p. 2n3 /0.08 torr 2-CN 4-Cl CH3 -0C4Hg(iSo) b.p. 190 /0.02 torr - 13 ~

:~.....

~53~

Compound Position of Rl 3 5 Physical constants the CN group . m.p. /b.p. C/torr ~Ith poslt on _ _ _ 26 2-CN 4-Cl CH3 -OC~ H9( s ec) oi l 27 2-CN 4-Cl CH3 -O-cycl ohexyl oi l 28 2-CN 4-Cl CH3 -O-phenyl m.p. 15529 2-CN 4-Cl CH3 -0-(CH2)2-0-CH3 oi l 2-CN 4-Cl CH3 -OC4Hg(tert) oi l 31 2-CN 4-Cl CH3 -0-CH2-CH-C-CH3 oi l 32 2-CN 4-Cl CH3 -0-CH2-CH=CH-CH3 oi l 33 2-CN -Cl CH3 -S-phenyl oi l 34 4-CN H CH3 -OC3H7(n) b.p. 190/0.01 torr 4-CN H CH3 -OC4Hg(n) b.p. 177-183 /0.015 torr 36 4-CN H CH3 -OC4Hg(iso) b.p. 203 /0.05 torr 37 4-CN 2-Cl CH3 -OC2H5 oi l 38 4-CN 2-Cl CH3 -OC4Hg(n) oil 39 2-CN 4-Cl CH3 -0-CH2~ Cl oil 2-CN 3-Cl CH3 -OCH3 m.p. 84-85 41 4-CN H CH3 (CH2)2 C 3 b.p. 188/0.04 42 2-CN 4-Cl CH3 -N(C113)2 i l 43 2-CN 4-Cl CH3 -S-C~I -COOC2H5 oi l 44 2-CN 4 -Cl CH 3 -NHCH3 m. p . 1 bO
C~13 2-CN 4-Cl CH3 -0-C11243 res i nous 46 2-CN 4-Cl CH3 -0-CH2-~ resi nous 47 2-CN 4-Cl CH3 O (CH2)4 3 viscous oil /C~13 48 2-CN 4-Cl CH3 -0-CH2-CII-C2H5 i 49 2-CN 4-Cl CH3 O (CH2)2 H( 3)2 i~
2-CN 4-Cl CH3 -0-C~12-C(CH3)3 i~

~i3~

Compound Position of R R R5 Physical constants the CN group 1 3 m.p. C/b.p. C/torr _ ___ _ 51 4-CN H CH3 CH3 oi l 52 2-CN 4-Cl CH3 CH3 oi l 53 4-CN H CH3 CH3 oi l 54 2-CN 4-Cl CH3 -0-CH2-CH(C2H5)2 oil 4-CN H CH3 -0-CH2-CH(C2H5)2 oi l 56 2-CN 4-Cl CH3 -SC113 58 2-CN '-CF3 CH3 -OCH3 m.p. 105-106 59 2-CN 4-CF CH -OH m.p. 158-162 2-CN 4-CF33 CH33 -C2'15 ~ 180 /0.65 61 2-CN 4-CF3 CH3 -OCH -CH=C112 b p 178 /0.018 62 2-CN 4-CF3 C~13 ( 2)2 3 b.p. 195/0.02 63 2-CN 4-CF3 CH3 -S-CH2-C~-CH2 b . p . 200/0 . 07 64 2-CN 4-CF3 CH3 -OCH2-C-CH oi l 2-CN 4-CF3 CH3 -OCH2-CII(CH3)2 m.p. 69-70 66 2-CN 4-CF3 CH3 OC3H7( ) oi l 67 2-CN 4-CF3 CH3 -OCH -C=CH2 oil 68 2-CN 4-CF3 c,~3 -N(C2H5)2 m.p. 115-119 69 2-CN 4-CF3 C~13 O-phenyl m.p. 97-99 2-CN 4-CF3 CH3 -OC4Hg( n) oil 71 2-CN b-CF3 CH3 -SC~3 b.p. 200-210 /0.4 72 4-CN 2-CF3 c,,3 -OCH3 73 4-CN H CH3 -OC3H7(iso) oil 74 4-CN H C113 -OC4Hg(sec. ) oi l 4-CN H C113 -SCH3 oi l . 76 4-CN 2-Cl CH3 -0-C3H7(n) oil 77 4-CN 2-Cl CH3 -OC3'17( i so) oi l ~s~

Co~pound PositiDil of Rl R R Physical constants the CN ~roup __ 3 5 m,p. C/b.p. C/torr 78 4-CH 2-Cl C~13 -OC~Hg( iso) oi l 79 4-CN . 2-Cl C1~3 -OC4H9(sec. ) oil 4-CN 2^Cl CH3 2 <C 11 oil 31 ~ CH 2-CI C113 __~ L

The compound methyl 4-(2'-cyano-4'-chlorophenoxy) -a- 3-chloro-phenoxy-propionate of the formula Cl ~ O ~ O-CH-COOCH3 CN Cl is prepared as an example of active compounds in which R2 represents halogen, and is obtained in the form of an oil.
The novel active substances (compounds) of the formula I
are stable compounds which are soluble in conventional organic solvents, such as alcohols, ethers, ketones, dimethyl formamide, dimethyl sulphoxide etc.
The compositions of the present invention are obtained in known manner by homogeneously mixing and grinding active substances of the general formula I with suitable carriers and/or additives, with or without the addition of antifoam agents, wetting agents, dispersants and/or solvents which are inert to the active substances. The active substances can be formulated as follows:

~ ~ 3 solid formulations:
dusts, tracking agents, granules (coated granules, impregnated granules and homogeneous granules);
active substance concentrates which are dispersible in water:
wettable powders, pastes, emulsions, emulsifiable concen~
trates;
liquid formulations: solut-.ions.
The concentration of ac~ive substance in the compositions of this invention is between 1 and 80 percent by weight. ~s circumstances may require, the active substances can also be applied in low concentrations of about 0.05 to 1 percent by weight.
The compositions of the present invention can be mixed with other biocidal active substances or compositions. Thus in addition to containing the cited compounds of the formula I, the compositions of the present invention can also contain, for example, insecticides, fungicides, bactericides, fungi-static agents, bacteriostatic agents, nematocides or further pesticides, in order to broaden the activity spectr~lm.

Granules The following substances are used to prepare 5% granules:
parts of one of the active substances of the formula I, 0.25 parts of epichlorohydrin, 0.25 parts of cetyl polyglycol ether, ~s~

3.50 parts of polyethylene glycol, 91 parts of kao]in (particle size 0.3 - 0.8 mm).
The active su~stance is mixed with epichlorohydrin and dissolved with 6 paxts of acetone, and the polyethylene glycol and cetyl polyglycol ether are then added. The resultant solution is sprayed on kaolin and subsequently evaporated in vacuo.

Wettable Powder The following constituents are used to prepare a) a 70% and b) a 10% wettable powder:
a~ 70 parts of methyl 4-(2',-cyano-4'-chlorophenoxy)-a-phenoxypropionate,

5 parts of sodium dibutylnaphthalene sulphate, 3 parts of naphthalenesulphonic acid/phenolsul-phonic acid/formaldehyde condensate (3:2:1), 10 parts of kaolin, 12 parts of Champagne chalk;
b) 10 parts of methyl 4-(2'-cyano-4'-trifluoromethyl-phenoxy)-a-phenoxypropionate, 3 parts of a mixture of the sodium salts of saturated fatty alcohol sulphates, 5 parts of naphthalenesulphonic acid/formaldehyde condensate.
82 parts of kaolin.
The respective active substance is applied to the ~ ~ 3~ ~ ~
corresponding carriers (kaolin and cllalk) and therl these are mixed and ground, to yield we~table powders of excellent wettability and suspension power. By diluting these wet~able powders with water it is possible to obtain suspensions containing 0.1 to 8% of active s~stance. These suspensions are suitable for controlling weeds in cultivat;ons of plants.
Paste The following substances are used to prepare a 45% paste:
45 parts o ethyl 4~ cyano-phenoxy)-a-phenoxy-propionate or one of the other cited active compounds of the formula I, 5 pa~ts of sodium aluminium silicate, 14 parts of cetyl polyglycol ether with 8 moles of ethylene oxide, l part of oleyl polyglycol ether with 5 moles o ethylene oxide, 2 parts of spindle oil, 10 parts o polyethylene glycole, 23 parts of water.
The active substance is intimately mixed with the additives in appropriate devices and ground~ A paste is ob-tained from which, by dilution with water, it is possible to manufacture suspensions of the desired concentration of active substance.

Emulsiiable ~oncentrate The ollowing ingredients are mixed to prepare a 25%
emulsiiable concentrate:

25 parts of isohutyl 4-(2'~cyano-4'-chlorophenoxy)-a-phenoxy-propionate or one of the other cited active compounds of the formula I, 5 par~s of a mixture o nonylphenolpolyoxyethylene and calcium dodecylbenzenesulphonate, 35 parts of 3,5,5 trimethyl-2-cyclohexen-1-one, 35 parts o~ dimethyl formamide.
This concentrate can be diluted with water to give emulsions in suitable concentra~ions o e.g. 0.1 to 10%. Such emulsions are suitable for controlling weeds in ~ultivations of plants.
The novel 4-phenoxy-a-phenoxyalkanecarboxylic acids which contain at least one cyano group in one phenyl nucleus and their derivatives of the formula I, and the compositions which contain them, have an excellent selective herbicidal action against grass-like weeds in a wide variety of cxops of culti-vated plants.
Since the novel active compounds destroy virtually only grass-like weeds and attack broad-lea~ed (dicotyledonous) plants only to an insigni~icant extent, they are accordingly suitable for controlling grass-like weeds in crops o~ all dicotyledonous cultivated plants, such as cot~on, soya, sugar ~eet, leguminosae, celery, clover, lucexnes, melons, cucumbers, tobacco etc. In addition, they exl~ibit a markedly better selectivity, for example in soya, cotton and sugar beet, than do the closely related chlorinated and trifluorom2thylated active substances of D~ OS 2,223,~9~ and of Belgian pa~ents 831,218 and ~31,469 wl~ich do not con~ain a cyano group. A
control of maize in soya cul~ures is also possible.
However, i~ is particularly surprising that the novel active compounds of the formula I also possess an outstanding selectivity in the control of grass-like weeds, especially o Panicum-like weeds, in cultures of monocotyledonous plants, such as cereals (~heat, barley etc.) and rice.
Accordingl~, panic-grasses of the genera S~taria, Echinochloa, Digitaria, Rottboellia and the like can also be controlled exceptionally well selectively in cultures of monocotyledonous plants, such as wheat and barley etc., aside from in soya.
The novel compounds also have an excellent action against other grass-like weeds, such as Alopecurus, Lolium, Apera, Agrostis etc.
An especially preferred field of use is the selective control of the problem weed Avena fatua (wild oats) and its related species in wheat, barley and sugar beet.
Although the novel active compounds of the formula I are effective in pre- and post emergent application, the post-emergent appllcation in the form of contact herbicides is preferred. But the pre-emergence use is also of interest.
The novel active compounds are preerably formulated for example as 25% wettable powders or for example 20%
emulsifiable concentrates and diluted with water, and applied ~ ~S 3~ ~ ~to the plant cultures in the post-ernergence stage.

Herbicidal act_ n on a~yin~ e active cornpounds after emergence of the plants (post-emer~ent applicati~
Different cultivated plants and grass-like weeds are reared from seeds in pots in a greenhouse until they have reached the 4- to 6-leaf stage. Then the plants are sprayed with aqueous active substance emulsions (obtained from a 20%
emulsifiable concentrate) in different rates o~ application corresponding to 8, 4, 2, 1 and O.S kg/hectare. The treated plants are then kept at optimum light, watering, temperature (22-~5C) and humidity (50~70% rela~ive humidity) conditions.
~valuation of the test was made 15 days after treatment using the following rating:
9 = plants undamaged (as untreated control plants) 1 = plants completely withered 8-2 - intermediate stages of damage.

Cultivated plants:
Hordeum (barley) Triticum (wheat) Oryza (rice) Glycine (soya) Gossypium (cotton) Beta (sugar beet) Grass-like weeds and undesi_ ble plants:
Avena fatua Loli~un perenne 3~

Alopecurus myos.
Zea (maize) Rottboellia exaltata Digitaria sang.
Setaria italica Echinochloa grus galli.
The result of the test showed that the tested active compounds of the invention of the formula I containing a cyano substituent exhibit a marlcedly better selectivity towards wheat, soya, cotton, sugar beet and rice in that they damage these cultivated plants very much less that the constitutionally closest kno~m compounds which do not contain a cyano group.

Claims (20)

WHAT WE CLAIM IS:

1. Novel herbicidally active, nuclear-substituted 4-phenoxy-.alpha.-phenoxy-alkanecarboxylic acid derivatives of the formula I

(I) wherein R1 represents hydrogen, halogen, the trifluoromethyl or cyano group, R2 represents hydrogen or halogen, each of R3 and R4 independently represents hydrogen or lower alkyl, and represents a OH, -O-cation, -O-alkyl, -O-alkoxy-alkyl, -S-alkyl, S-alkenyl, -S-CH2-COO-alkyl, -O-alkenyl, -O-alkynyl, -O-cycloalkyl, -O-alkyl-N(dialkyl) group, an unsubstituted or substituted benzyloxy, phenoxy or phenylthio radical, and NH2, NH-alkyl, -N(dialkyl) or .

2. Alkanecarboxylic acid derivatives according to claim 1, wherein R2 in formula I represents hydrogen.

3. Alkanecarboxylic acid derivatives according to claim 1 or 2, wherein in formula I represents a substituent which is different from hydrogen.

4. Alkanecarboxylic acid derivatives according to claim 1 or 2, wherein the substituents R1 and CN are in the ortho- and para-position of the phenoxy radical in question.

5. Alkanecarboxylic acid esters according to claim 1 or 2, wherein R
represents a chlorine atom or the trifluoromethyl group.

6. Alkanecarboxylic acid derivatives according to claim 1, wherein R2 and R4 represent hydrogen and R3 represents a methyl radical.

7. Methyl 4-(2'-cyano-4'-chlorophenoxy)-.alpha.-phenoxypropionate..

8. Isobutyl 4-(2'-cyano-4'-chlorophenoxy)-.alpha.-phenoxypropionate..

9. Methyl and ethyl 4-(4'-cyanophenoxy)-.alpha.-phenoxypropionate.

10. Methyl 4-(4'-trifluoromethyl-2'-cyanophenoxy)-.alpha.-phenoxypropionate.

11. A process for the manufacture of 4-phenoxy-.alpha.-phenoxy-alkanecarboxylic acid derivatives of the formula I of claim 1, which comprises (a) reacting a halogenobenzonitrile of the formula II

(II) wherein Hal represents a halogen atom and R1 is as defined in formula I with a 4-hydroxy-.alpha.-phenoxycarboxylic acid derivative of the formula III

(III) in which R2, R3, R4 and R5 are as defined in formula I, in the presence of a base;
(b) reacting a substituted 4-hydroxydiphenyl ether of the formula IV

(IV) in which R1 and R2 are as defined in formula I with an .alpha.-halo-genoalkanecarboxylic acid derivative of the formula V, (V) in which R3, R4 and R5 are as defined in formula I and Hal represents a halogen atom, in the presence of a base; or (c) reacting a halogenated 4-phenoxy-.alpha.-phenoxy-alkanecarboxylic acid derivative of the formula VI

(VI) in which Hal represents a halogen atom and R1 to R5 are as de-fined in formula I, is reacted with potassium or sodium cyanide, optionally in a polar solvent and in the presence of a catalyst which activates the halogen atom.

12. A process according to claim 11(c), wherein the catalyst is Ni[P(C6H5)3]4, and the reaction is carried out with the exclusion of air and under a protective gas atmosphere.

13. A method for the selective control of grass-like weeds in crops of dicotyledonous and monocotyledonous cultivated plants, which comprises treating the sown cultivated areas be-fore or after emergence with a herbicidal composition which con-tains as active component a 4-phenoxy-.alpha.-phenoxy-carboxylic acid derivative of the formula I of claim l.

14. A method according to claim 13 which comprises the post-emergent application of a composition which contains as active component a 4-(cyanophenoxy)-.alpha.-phenoxy-alkanecarboxylic acid ester.

15. A method according to claim 13 or 14 for the post-emergent control of Avena fatua and Panicum-like weeds in wheat, soya, cotton or sugar beet which comprises the use of a 4-(cyano-chlorophelnoxy)-.alpha.-phenoxy-propionic acid ester as active component of the composition applied.

16. A method according to claim 13 or 14 for the post-emergent control of Avena fatua and Panicum-like weeds in cereals, soya, cotton or sugar beet, which comprises the use of a 4-(trifluoromethyl-cyanophenoxy)-.alpha.-phenoxy-propionic acid ester as active component of the composi-tion applied.

17. A method according to claim 13 or 14 for the postemergent control of Avena fatua and Panicum-like weeds in cereals, soya, cotton or sugar beet, which comprises the use of a herbicidal composition which contains as active component methyl or isobutyl4-(2'-cyano-4'-chlorophenoxy)-.alpha.-phenoxy-propionatee.

18. Compounds of the formula:

wherein R is hydroxy, -0-cation, lower alkoxy or lower alkenyloxy.

19. The compound:

20. Compounds of the formula:

wherein Am represents amino, lower alkylamino and dilower alkylamino.